The application of anhydrous ammonia to the soil is generally achieved by the use of tractor mounted equipment. A reservoir of anhydrous ammonia is mounted on the tractor, and a series of knives are pulled through the soil behind the tractor. Anhydrous ammonia travels from the reservoir, through a metering device, to a distribution manifold, and from there to tubes attached to the rear of the knives. As the knives are dragged through the soil behind the tractor the ammonia is directed out through holes in the tubes into the soil.
There are a number of different designs for the distribution manifold. They commonly have a cylindrical body with one axial inlet, and a number of radial outlets. In some designs a cone is provided inside the manifold immediately below the inlet to divert the incoming stream towards the radially arranged outlets.
There have been longstanding difficulties in calibrating anhydrous ammonia applicators and ensuring an even rate of delivery to the soil. An application distribution error rate of about 16% has in the past been found to be typical. To overcome this problem, operators often increase the application rate to ensure that all areas receive a full application. This may cause off-site pollution by nitrogen entering the ground water, and in addition is wasteful.